Measuring, indicating, and recording instrument



March 1939- T. R. HARRISON ET AL 2,150,502

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March 14, 1939. T. R HARRISON ET AL 2,150,502

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March 14, 1939. T. R, HARR ON ET'AL 2,150,502

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March 14, 1939 'r. R. HARRISON ETAL MEASURING, INDICATING, AND RECORDINGINSTRUMENT Filed June 25, 1931 18 Sheets-Sheet 14 FIG. 3211/:

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March 14, 1939. T. R. HARRISON ET AL I MEASURING, INDICATING, ANDRECORDING INSTRUMENT File'd June 23, 1951 18 Sheets-Sheet 15 March 14,1939. T. R. HARRISON ETA].

MEASURING, INDICATING, AND RECORDING INSTRUMENT l8 Sheets-Sheet l6INVENTORS. IITRHarrzsazz,

Filed June 23, 1931 March 14, 1939- T. R. HARRISON ET AL 2,150,502

MEASURING, INDICATING, AND RECORDING INSTRUMENT Filed June 25, 1931 18Sheets-Sheet 1 March 14, 1939. T. R. HARRISON ET AL 0 MEASURING,INDICATING, AND RECORDING INSTRUMENT Filed June 23, 1931 18 Sheets-Sheet18 IN V EN TORS. Tlifiarrzson,

Patented Mar. 14, 1939 UNITED STATES PATENT OFFICE MEASURING,INDICATING, AND RECORD- ING INSTRUMENT tion of Pennsylvania ApplicationJune 23, 1931, Serial No. 546,290

20 Claims.

This invention relates to measuring instruments and more especially toimprovements in potentiometric measuring and recording instruments.

Potentiometers of the automatic balancing type are well known and havebeen available in commercial form for many years. Such potentiometers,while affording a more or less satisfactory service and being of adesign and construction adapted for a more or less satisfactory facilityand cost of manufacture, fall short of the most desirable form andconstruction of potentiometer, both from the standpoint of operation andservice, and facility and cost of construction and maintenance.

It is the object of this invention to provide a measuring instrument ofthe potentiometer type involving numerous improvements in the individualparts which collectively make up the potentiometer, and also in therelative arrangement and efliciency of cooperation of the parts. Thisinvention comprises improvements in the galvanometer constructionaffording a simpler and less expensive mode of manufacture, provid ing asimpler galvanometer assembly having a maximum of accessibility foradjustment and service and a minimum of constructional features subjectto failure in operation. This invention also includes the provision ofan improved form of mechanism for automatically balancing thepotentiometric circuit adapted to simplify practice in manufacture, toincrease efficiency and smoothness of operation, and to provide greaterindependence of failure in operation. The invention also comprises theprovision for indicating and/or recording thevalue of the quantitymeasured by the potentiometer system, which is a simplified constructionand an improvement in efliciency of operation. The invention alsoincludes improvements in case construction for containing thepotentiometer mechanism, and improvements in standard cell constructionand mounting. This invention provides such improved forms ofconstruction of parts and assembly thereof, as permits the extensive useof sheet metal stamping and parts molded from heat plastic materials sothat'the formed parts may be combined into the complete potentiometerwith a minimum of hand or machine operation. In'addition, such parts asthe galvanometer assembly, the galvanometer position gauging assembly,and the slide wire assembly, have been made as separate units completein themselves for mounting in a frame, and so constructed that whenassembled interfit in operative relation, thus facilitating greatly themanufacture, assembly, and service of such an instrument. Other objectsand advantages of. the invention appear in the detailed descriptionwhich follows. 5

In the accompanying drawings,

Fig. 1 shows the front elevation of the potentiometer of this inventionwith parts broken away and in section.

Fig. 2 shows the top plan view of the instrul0 ment mechanism assemblywith parts broken away and in section.

Fig. 3 shows a partial rear elevation with parts broken away and insection.

Fig. 4 shows, in perspective, the galvanometer l5 assembly with theparts separated for clearness.

Figs. 5 and 6 show in front and rear elevation respectively, thegalvanometer unit.

Fig. 7 shows, in perspective, the molding which forms an element in thegalvanometer assembly. 20

Figs. 8 and .9 show details, in top plan and perspective respectively,of the galvanometer zero adjusting mechanism.

Figs. 10 and 11 show detail views in perspective and in section,respectively, showing the galvanometer pointer and coil construction.

Fig. 12 is a perspective view of the galvanometer position gaugingassembly.

Fig. 13 is a perspective view similar to Fig. 12, taken from anotherangle.

Fig. 14 is a detail view in elevation of the galvanometer positiongauging assembly.

Figs. 15, 16, and 17 are perspective views of the parts whichcollectively make up the galvanometer position gauging assembly.

Fig. 18 is a cross sectional view of the slide wire unit and associatedparts showing the assembled relation of the unit to the frame andstandard cell.

Fig. 19 is a top plan view, partly broken away and in section, of theslide wire unit.

Fig. 20 is a view, inv front elevation, of the slide Wire assembly.

Fig. 21 is a detail view of the slide wire assembly.

Fig. 22 is a view in perspective showing the electrical connections forthe slide wire unit.

Fig. 23 is a view in perspective of the operating parts of thepotentiometer with the parts relatively displaced to show more clearlytheir operation.

Fig. 24 is a detail view of the secondary pointer.

Fig. 25 is a detail view of the chart drive IOll construction.

Fig. 26 is a view in end elevation of the potentiometer showing thedrive mechanism for automatically operating the potentiometer.

Fig. 27 is a view in elevation similar to Fig. 26, but taken in theopposite direction.

Fig. 28 is a detail view of the mechanism for operating the chart driveroll.

Figs. 29, 30, 31, and 32 are views in perspective and elevation,illustrating the operating parts of the potentiometer drive mechanism atdifferent stages of operation.

Fig. 33 is a sectional detail view showing the construction of the chartre-roll.

Fig. 34 is a detail view, partly in elevation and partly in section,showing the latch construction for securing the instrument in properposition within its casing.

Fig. 35 is a bottom plan view 01' the terminal box.

Fig. 36 is a top view, in perspective, of the terminal box showing partsin displaced position.

Fig. 3'7 is a detail in section showing the terminal mountingconstruction.

Fig. 38 is a view in side elevation broken away and showing operatingparts for multiple recording.

Fig. 39 is a view similar to Fig. 38 showing the parts in a differentstage of operation.

Fig. 40 is a view, in perspective, showing parts of the multiplerecording mechanism.

Fig. 41 is a detail view, in section, showing the mounting for theribbon bobbin.

Fig. 42 is a detail in perspective showing features of the humiditycompensator.

Fig. 43 is a diagrammatic view of a potentiometer circuit adapted foruse with the potentiometer of this invention.

potentiometer circuit Referring to Fig. 43, I designates a substantiallyconstant source oi. electromotive force such as an ordinary dry cellconnected in series with an adjustable resistor 2, the adjustment ofwhich is adapted to vary the current flow in the circuit containing thecell I, a ballast resistor 3, a slide wire 4, another ballast resistor5, a calibrating resistor 8, the value and manner of connection of whichmay be varied in order to vary the measuring range of the potentiometercircuit, completing the series of circuit. A shunt circuit containingresistors I and 8, is provided. The resistor I is included in themeasuring circuit completed through resistor 9, galvanometer Ill, switchI I, switch contact I2, conductors I3 and I4, across which are connecteda source of potential such as a thermocouple I5, the value of which isto be measured, conductor I6, resistor I! and sliding contact I8, totheslide wire 4. By making the resistor 1 of a suitable temperaturecoefficient of electrical resistance, the variation in temperature of acold junction may be automatically compensated for, as is well known inthe art. A resistor 8 is included inan auxiliary circuit extending fromresistor 8 through resistor I9, standard cell 20, switch contact 2|,switch II, galvanometer III, resistor 8, thus completing the circuit. Aresistor 22' may be shunted about the galvanometer I0 in order toproperly damp its movement when the switch II is thrown into engagementwith the contact 2| and at the same time engages contact 22. Inoperation the source of electromotive force I supplies a steady currentthrough slide wire resistor 4, thereby creating a definite potentialdrop across that resistor. The circuit including the thermocouple I5applies an electromotive force on the slide wire 4 in a direction suchas to oppose that created by the cell I. By adjusting the slidingcontact I8 along the resistor 4, a point on the resistor 4 is reachedwhere the potential of the thermocouple applied to the resistor 4 isequal and opposite to the potential of the resistor 4 at that point. Atsuch time the galvanometer I0, which is normally connected in circuitwith the thermocouple I5 by virtue of a normally closed position of theswitch I I, will have a zero deflection. Variations in the value of theelectromotive force of the thermocouple cause deflection of thegalvanometer In in a direction depending upon whether the variation isan increase or a decrease from that value for which the potentiometersystem is previously balanced. The contact I8 may be adjusted again tobring the galvanometer into a position which corresponds to a balancedcondition of the measuring system. When the potentiometer circuit isunbalanced a current, due to the thermocouple, flows through the circuitincluding the resistor 4, and corresponding changes in the position ofthe .contact I8 to balance the circuit, thereby varies the amount ofelectrical resistance due to resistor 4 which is included in thethermocouple and galvanometercircuit tending to change the constant ofthe galvanometer circuit.

The resistor I1 is connected in series in the thermocouple andgalvanometer circuit in a manner such that additional resistance isadded from resistor I1 when a like amount of resistance is eliminatedfrom resistor 4 by movement of contact I8, thereby maintaining aconstant electrical resistance in the thermocouple and galvanometercircuit so as to maintain an unvarying 'galvanometer constant throughoutthe measuring range of the potentiometer.

Inasmuch as the cell I tends to deteriorate slightly with age and use,it is necessary from time to time to adjust the resistor 2 in order tomaintain a predetermined current flowing through the slide wire resistor4. For standardizing the current flowing in the slide wire resistor,switch II is adjusted into engagement with com tacts 2| and 22, therebyconnecting the galvanometer ID in a circuit which. includes the standardcell 20 as a source of electromotive force arranged to oppose thepotential drop across the resistor 8 due to the current flowing in theresistor 8 from the cell I. Variations from the standard in the currentflowing through resistor 8 from the cell I, cause a deflection of thegal vanometer III from the position of zero deflection. The resistor 2is then adjusted to bring the galvanometer to a position of zerodeflection which corresponds to a balance between the potential shown asapplied to the use of thermocouplesfor measuring temperature variation.As shown in Fig. 43, a plurality of thermocouples I5 are illustrated,and a switch 23 diagrammatically illustrated by which any one of thethermo-

